Various optically-powered sensor systems exist today. U.S. Pat. No. 4,820,916 to Patriquin discusses one such system, in which optical energy is transmitted along a bus for distribution to sensors of the system. Return pulses from the sensors likewise are transmitted on the bus to a system controller. Sensor-specific time delays are provided to produce a pre-determined, time-multiplexed sequence of the return pulses.
U.S. Pat. No. 4,963,729 to Spillman, et al., discloses techniques for improving signal conditioning in optically-powered sensor systems. As with the system of the Patriquin patent, that of the Spillman patent transmits optical energy along a bus for distribution to sensors of the system. The bus also transmits return pulses from the sensors.
Yet another optically-powered sensor system is identified in U.S. Pat. No. 5,223,707 to Bjork. In some versions of the system, a controller may provide optical power to sensors and receive optical signals from the sensor locations on a single optical fiber. Alternatively, multiple optical fibers may be employed. Protocols are described which allow multiple sensors to communicate with a controller over a single optical fiber.
U.S. Pat. No. 7,965,948 to Bugash, et al., finally, also addresses using a single fiber and systems for “receiving a light power signal via the single fiber optic . . . and, in response to a pause in the received light power signal, transmitting a light data signal via the single optical fiber.” The systems may be deployed in aircraft fuel tanks, with optical fibers used in lieu of electrical wires. Incorporated herein in their entireties by this reference are the contents of the Patriquin, Spillman, Bjork, and Bugash patents.
Absent from any of these patents is, for example, any method of detecting or predicting breakage of an optical fiber. Likewise absent, therefore, is any systematic reaction to fiber breakage, which could result in injury should a human eye be exposed to an unattenuated light signal emanating from a broken fiber. Further absent from patents of this sort is any electronic safety barrier circuitry designed to limit supplied power below accepted maximums for explosive environments. Power-optimizing schemes in which sensors act based on available power rather than directly on command of a controller also are omitted; consequently, no extra energy (for “worst-case” scenarios) need necessarily be sent.